Catalytic biomass pyrolysis process

ABSTRACT

Described herein are processes for converting a biomass starting material (such as lignocellulosic materials) into a low oxygen containing, stable liquid intermediate that can be refined to make liquid hydrocarbon fuels. More specifically, the process can be a catalytic biomass pyrolysis process wherein an oxygen removing catalyst is employed in the reactor while the biomass is subjected to pyrolysis conditions. The stream exiting the pyrolysis reactor comprises bio-oil having a low oxygen content, and such stream may be subjected to further steps, such as separation and/or condensation to isolate the bio-oil.

FIELD OF THE DISCLOSURE

The present disclosure is directed to processes for biomass pyrolysis.More particularly, the processes provides catalytic pyrolysis methodsfor converting biomass to a low oxygen content bio-crude that may befurther processed to prepare useful products, such as biofuels.

BACKGROUND

To supplement or even replace conventional fuels derived from decreasingpetroleum supplies, fuels formed from renewable sources, particularlybiological sources (i.e., so-called “biofuels”), are being sought anddeveloped. Currently, biofuels, such as ethanol, are produced largelyfrom grains, but a large, untapped resource of plant biomass exists inthe form of lignocellulosic material. This untapped resource isestimated to encompass more than a billion tons per year (see U.S.Department of Energy (2011) U.S. Billion-Ton Update: Biomass Supply fora Bioenergy and Bioproducts Industry, Perlack and Stokes,ORNL/TM-2011/224, Oak Ridge National Laboratory, Oak Ridge, Tenn., p.227—available online athttp://www1.eere.energy.gov/biomass/pdfs/billion_ton_update.pdf).Although age-old processes are available for converting the starchcontent of grain into sugars, which can then be converted to ethanol,the conversion of lignocellulose to biofuel is much more difficult.

Pyrolysis is a thermochemical processing option for producing liquidtransportation fuels from biomass. Traditional biomass flash pyrolysisprocesses have demonstrated a roughly 70% liquid product yield; however,this pyrolysis oil product has limited use without additional upgradingor refining. Current, commercial biomass pyrolysis processes areprimarily used to produce commodity chemicals for the food productsindustry. Fuel uses for raw pyrolysis oils have been demonstrated forelectric power production in boilers, diesel engines, and (with limitedsuccess) in turbines.

Biomass pyrolysis is the thermal depolymerization of biomass at modesttemperatures in the absence of added oxygen to produce a mixture ofsolid, liquid, and gaseous products depending on the pyrolysistemperature and residence time. Charcoal yields of up to 35% can beachieved for slow pyrolysis at low temperature, high pressure, and longresidence time. Flash pyrolysis is used to optimize the liquid productsas an oil known as bio-crude or bio-oil. High heating rates and shortresidence times enable rapid biomass pyrolysis while minimizing vaporcracking to optimize liquid product yields with up to about 70%efficiency on a weight basis.

Bio-oil can be upgraded either at the source prior to full production orafter the formation of the liquid product. To date, the two most popularmethods in post-production upgrading are adapted from traditionalhydrocarbon processing. These processes are bio-oil cracking over solidacid catalysts and hydrotreating in the presence of high pressurehydrogen and a hydrodesulfurization (HDS) catalyst. Although both ofthese processes have the potential to bring down the oxygen content to adesirable level, it should be noted that both cracking and hydrotreatingare accompanied by the loss of hydrogen (as H₂O) and carbon (as CO₂ orCO) from the bio-oil.

Hydrodeoxygenation (HDO) is carried out at high temperatures (200 to450° C.) and in the presence of a typical HDO catalysts, most commonlyCoMo or NiMo sulfide catalysts. Loss of hydrogen as water duringhydrotreating significantly lowers the hydrogen content of bio-oil. Inorder to offset this, hydrogen typically is externally added during theprocess at high pressures (e.g., 3 to 12 MPa). As a result, externalhydrogen demand can be high—e.g., calculated to be on the order of 41 kgper ton of biomass. Since hydrogen is added to the process at some cost,such a high hydrogen demand makes HDO uneconomical. HDO can beconceptually characterized as follows:

C₆H₈O₄+6H₂→6CH₂+4H₂O

C₆H₈O₄+4.5H₂→6CH_(1.5)+4H₂O

Cracking reactions in bio-oils can occur at atmospheric pressure usingan acid catalyst. In catalytic cracking, deoxygenation can take place asa result of one or more of dehydration, decarboxylation, anddecarbonylation reactions. Decarboxylation specifically leads to theincrease in hydrogen-to-carbon (H/C) ratio, thereby increasing theheating value or energy density. Dehydration and decarboxylationreactions can be controlled by modifying the reaction temperature. Ingeneral, lower temperatures favor a dehydration reaction, whereas highertemperatures favor a decarboxylation reaction.

Many catalysts have been exploited for the catalytic cracking ofpyrolysis oils including zeolites (e.g., H-ZSM-5 and ultrastableY-zeolite), mesoporous materials like MCM-41 and Al-MCM-41, andheteropolyacids (HPAs). The main disadvantage associated withheteropolyacids is that they are fairly soluble in polar solvents andlose their activity at higher temperatures by losing structuralintegrity. Major components of bio-oils (phenols, aldehydes, andcarboxylic acids) have low reactivity on ZSM-5 and undergo thermaldecomposition producing coke.

Zeolite catalysts also deactivate quickly by coke formation from thedecomposition of large organic molecules present in the bio-oil. Thisblocks the pores and decreases the number of available catalytic sites.The large amount of water vapor in bio-oils also leads to dealuminationof zeolite materials causing loss of surface area and irreversibledeactivation. In comparison, catalytic cracking is regarded as a cheaperroute of converting oxygenated feedstocks to lighter fractions. Thisprocess, however, leads to higher coke formation (about 8-25 wt %).Unlike the petroleum crude oil upgrading, upgrading of high oxygencontent (about 35-50 wt % on a dry basis—i.e., excluding oxygen from anywater that may be present) bio-crude into suitable quality biofuelsusing traditional catalysts will result in significant weight loss ofhydrogen and carbon and subsequently decrease the conversion efficiency.During these processes, only a fraction of the carbon present in the rawbio-oil ends up in the upgraded bio-oil. Losses to carbon oxide, andcarbon deposition on the catalyst, and system fouling substantiallyreduce the biomass carbon conversion to final products when upgradingfast pyrolysis bio-oil.

Similar to petroleum crude oil processes, key issues such as cokedeposition and catalyst stability still remain for biomass processing orbio-crude upgrading over the conventional catalysts. In some cases, theconventional catalysts may no longer be suitable for bio-crude orbiomass processing. For example, due to low sulfur content in theinitial biomass feedstock, the conventional sulfided CoMo HDS catalystsused extensively for hydroprocessing in oil refining may not be suitablefor bio-crude hydrotreating. The low sulfur environment may cause thereduction of sulfided Co or Ni catalysts to the metal state followed byrapid coke deposition and catalyst deactivation. The necessity to addsulfur donor compounds to the feedstock to maintain the catalyticactivity, however, may complicate the process and potentially add sulfurto the fuel product. Cracking over acidic catalysts like zeolites andsupported metal oxides (Al₂O₃), which have the tendency to undergo rapiddeactivation due to coking, leads to relatively high yields of lighthydrocarbons. Thus, an improved or novel catalyst with better stabilityfor coke formation resistance and higher selectivity towards bio-oilformation will be needed for biomass conversion to bio-oil.

Using dehydration of a fast pyrolysis bio-oil to achieve removal ofoxygen (the main product of HDO and cracking over acid catalysts) wouldrequire over 80% of the hydrogen in the bio-oil if no external hydrogenwere supplied. As a result, a significant amount of hydrogen input isneeded to make up for the hydrogen loss as water and thus increase theH/C ratio to a value in the range of 1.9 to 2.4. For example,approximately 20 to 45 kg of hydrogen is required for one ton of biomassto achieve a theoretical yield of 75 to 98 gallons of biofuel per ton ofbiomass. A number of analyses reveal that upgrading of bio-crude throughhydrotreating is not economically attractive because of the high demandof hydrogen. It can also be seen that similar issues will occur to theupgrading of bio-crude through conventional cracking over acidcatalysts. Therefore, conventional methodologies such as hydrotreatingand cracking do not allow higher efficiencies to be achieved during theconversion of biomass to upgraded bio-oil. In order to achieve highconversion efficiencies, a catalytic biomass pyrolysis process thatselectively deoxygenates the biomass with minimal hydrogen and carbonloss can be advantageous. Thus, there remains a need in the art foruseful processes for transformation of biomass into high valuecommodities and/or stable intermediates therefor.

Recent studies have detailed the potential of catalytically upgradingcondensed bio-oil into gasoline range hydrocarbons. For example, U.S.Pat. Pub. No. 2009/7578927 to T. Marker et al. describes work with theNational Renewable Energy Laboratory (NREL) and the Pacific NorthwestNational Laboratory (PNNL) for developing a two-stage hydrotreatingprocess to upgrade raw bio-oil into gasoline and diesel. This workfocused on separating the pyrolytic lignin fraction of whole bio-oil,blending this fraction with vegetable oils and free fatty acids to forma slurry, and injecting the slurry into a hydrotreating reactor/processwith nickel catalysts.

Another process option is catalytic biomass pyrolysis to catalyticallymodify the composition of the bio-crude intermediate to improve theefficiency of the upgrading step. For example, U.S. Pat. Pub. No.2010/0105970 to P. O'Conner et al. describes catalytic pyrolysis in athree-riser FCC-type process. The process first consisted of mixing abase catalyst with biomass in a pretreatment step and reacting at atemperature of 200 to 350° C. The second step consisted of acid catalystcracking and deoxygenation at 350 to 400° C. where the products from thefirst step were added to a reactor with a solid acid catalyst. Theprocess further made use of a regenerator operating at temperatures upto 800° C. to burn the coke deposits on the catalyst and provide processheat.

U.S. Pat. Pub. No. 2009/0227823 to G. Huber described catalyticpyrolysis using zeolites that are unpromoted or are promoted withmetals. The pyrolysis was carried out at a temperature of 500 to 600° C.and a pressure of 1 to 4 atm (approximately 101 to 405 KPa) to produce ahighly aromatic product.

Publication WO 2009/018531 to F. Agblevor described the use of catalyticpyrolysis to selectively convert the cellulose and hemicellulosefractions of biomass to light gases and leave behind pyrolytic lignin.The methods used H-ZSM-5 and sulfated zirconia catalysts in a fluidizedbed reactor to obtain an overall bio-oil yield of 18-21%.

SUMMARY OF THE DISCLOSURE

The present disclosure provides catalytic biomass pyrolysis processesthat are beneficial for forming a liquid bio-oil pyrolysis product richin hydrocarbons and simultaneously low in oxygen content. The low oxygencontent makes the bio-oil particularly beneficial in that it is morethermally stable than bio-oil product from known pyrolysis reactions.Likewise, the low oxygen content bio-oil prepared according to thepresent disclosure may immediately be subjected to refining to preparebiofuels without the need for intermediate steps, such as deoxygenationor stabilization by mild hydrotreating. Further, the bio-oil preparedaccording to the disclosure may be blended with a petroleum oil streamand thus subjected to refining or other processes or uses common topetroleum oil. Still further, the inventive process is useful becausethe catalytic pyrolysis process improves carbon conversion efficiency incomparison to known integrated pyrolysis processes for biofuelproduction. Particularly, typical post-pyrolysis treatments to removeoxygen also remove some of carbon (i.e., in the form of coke deposits,CO, or CO₂), and the presently disclosed subject matter overcomes thisproblem. Thus, the pyrolysis product is in a stable, intermediate formthat is ready for refining and that maintains a high percentage of thecarbon originally present in the biomass starting material. Thiscorrelates to a more efficient pyrolysis process wherein a greatercontent of useful bio-oil is produced in relation to the amount ofbiomass used in the pyrolysis reaction. In certain embodiments, thereaction can provide for selective removal of oxygen from the biomassstarting material via one or both of direct catalytic deoxygenation andindirect deoxygenation through catalytic hydrogen production and in situhydrodeoxygenation.

In one embodiment, the disclosure thus provides a catalytic biomasspyrolysis process that comprises reacting a biomass starting materialunder pyrolysis conditions in the presence of a catalyst to form astream comprising a pyrolysis product. The stream can be divided into asolids component or fraction (i.e., containing the catalyst and anypyrolysis product solids—e.g., char) and a vapor (condensable) and gas(non-condensable) component or fraction. In specific embodiments, thevapor and gas fraction of the pyrolysis product has an oxygen content ofabout 20% or less by weight, preferably about 10% or less by weight (ona dry weight basis). Since at least a portion of the vapor and gasfraction may be condensed to form a bio-oil, the bio-oil formed from theprocess likewise can have an oxygen content of about 20% or less byweight, preferably about 10% or less by weight on a dry weight basis.

The disclosed subject matter is beneficial in that a wide variety ofstarting materials may be used as the feedstock in the pyrolysisprocess. Particularly, any type of biomass may be used. In specificembodiments, the biomass starting material used in the catalyticpyrolysis process can comprise a lignocellulosic material. In someembodiments, the biomass starting material can be characterized as beingparticularized and can have an average particle size of about 25 mm orless. In particular embodiments, the biomass starting material can havean average particle size of about 0.1 mm to about 25 mm.

The inventive process also can be defined by the use of a catalyst inthe actual pyrolysis step. In other words, the catalyst material that isused is combined with the biomass starting material in the pyrolysisreactor. Preferably, the catalyst is a material that promotesdeoxygenation of the pyrolysis products prior to separation of thecatalyst from the reaction products. Thus, the catalyst can be definedas an oxygen-removing agent. Such deoxygenation specifically can takeplace in the reactor under the pyrolysis conditions. In specificembodiments, the catalyst can comprise an iron oxide material. Further,the catalyst can be a mixed metal oxide, such as a bifunctionalcatalyst. Preferably, the bifunctional catalyst can be a material thatis useful to convert any water vapor formed during biomass pyrolysisinto hydrogen to provide a reactive environment for hydrodeoxygenationand also be useful to remove oxygen from biomass pyrolysis vaporswithout removing carbon.

In certain embodiments, the catalyst can comprise a mixture of ironoxide and tin oxide. The catalyst may be defined as comprising a mixtureof iron oxide and a metallic oxide promoter. For example, the promotercan be selected from the group consisting of chromium oxide, nickeloxide, manganese oxide, cobalt oxide, molybdenum oxide, and combinationsthereof. In some embodiments, the catalyst can be defined as being abifunctional catalyst. Further, the catalyst can comprise a supportedmetal or reduced metal oxide catalyst with variable valence states.Preferably, the catalyst is regenerable and is insensitive to ashpresent in the biomass or formed in the pyrolysis process.

The process can comprise feeding the biomass starting material into areactor wherein the biomass is subjected to the pyrolysis conditions inthe presence of the catalyst. The biomass starting material can be fedinto the reactor without premixing with the catalyst (which can providecharacteristics of a heat transfer medium). Other, non-catalyst heattransfer media also can be used, such as alumina, silica, olivine, andsands.

The catalytic biomass pyrolysis reaction can be carried out in a varietyof different types of reactors. Preferably, the reactor is a fluid-typereactor, such as a fluidized bed or a transport reactor. In oneembodiment, a riser reactor may be used. The biomass starting materialcan be transported through the reactor at a defined rate—e.g., a ratesuch that the residence time is less than defined time, such as about 5seconds or less.

Preferably, the reactor used is one that is capable of achieving thenecessary pyrolysis conditions to form a reaction product with thebeneficial characteristics described herein, such as low oxygen contentand high carbon conversion efficiency. Specifically, it can bebeneficial to use a reactor that is adapted for relatively shortresidence times of the biomass and the catalyst in the reactor, as notedabove. Another pyrolysis condition to be considered is reactiontemperature. In specific embodiments, the reacting of the biomass in thepresence of the catalyst can be carried out at a temperature of about200° C. to about 700° C. or a temperature of about 550° C. or less. Inother embodiments, the reacting of the biomass can be carried out at apressure of up to about 25 bar (2.5 MPa). In some embodiments, reactingcan be carried out at ambient pressure to near ambient pressure. Stillfurther, it can be useful for the biomass and the catalyst to becombined in the reactor in a specific mass ratio. In some embodiments,the catalyst and the biomass can be provided in a mass ratio of about1:1 to about 100:1.

As noted above, the pyrolysis process of the disclosure can compriseseparation of the pyrolysis products into two or more differentfractions. This can comprise transferring the stream comprising thepyrolysis product to a separator. In some embodiments, the stream may beseparated into a vapor and gas fraction and a solids fraction, whichcomprises solid reaction products and the catalyst. The inventive methodalso can comprise regenerating and recycling the catalyst into thepyrolysis process. In some embodiments, this also may includetransferring the catalyst from the separator through a reducing zoneprior to re-introduction into the reactor.

In other embodiments, the present disclosure further can provide acatalytic biomass pyrolysis system. In particular embodiments, suchsystem can comprise: a reactor adapted for combining a biomass with acatalyst under pyrolysis conditions to form a pyrolysis reaction stream;a separation unit in fluid connection with the reactor and adapted toform a first stream comprising a solids fraction from the pyrolysisreaction stream and a second stream comprising a vapors fraction fromthe pyrolysis reaction stream; a condenser unit in fluid communicationwith the separation unit and adapted to condense a bio-crude from thevapors in the second stream separate from a gas component of the secondstream; an optional liquid separator unit in fluid communication withthe condenser unit and adapted to separate water or another liquid fromthe bio-crude; a catalyst regeneration unit in fluid communication withthe separation unit and adapted to remove non-catalyst solids from thesolid catalyst present in the first stream; a reduction unit in fluidcommunication with the catalyst regeneration unit and adapted to reduceoxidized catalyst received from the catalyst regeneration unit; and acatalyst delivery stream adapted to deliver reduced catalyst from thereduction unit to the reactor.

The system can comprise an oxidant stream in fluid communication withthe catalyst regeneration unit and adapted to deliver an oxidant to thecatalyst regeneration unit. The condenser unit can be in fluidcommunication with the reduction unit via a gas flow stream adapted totransfer a portion of the gas component of the second stream to thereduction unit. The catalytic biomass pyrolysis system can comprise ablower unit interposed between and in fluid communication with thecondenser unit and the reduction unit. The catalytic biomass pyrolysissystem can comprise a biomass preparation unit in fluid communicationwith the reactor and adapted to transfer the biomass to the reactor. Thebiomass preparation unit can be adapted to particularize a solid biomassto a size of about 25 mm or less. The reactor of the catalytic biomasspyrolysis system can be adapted to combine the catalyst and the biomassin a ratio of about 1:1 to about 100:1 based on mass. The reactor can bea transport reactor. The reactor can be adapted to accommodate flow ofthe biomass therethrough with a residence time of about 5 seconds orless. The reactor can be adapted to a function at a temperature of about200° C. to about 700° C. or at a temperature of about 550° C. or less.The reactor can be adapted to function at a pressure of up to about 25bar (2.5 MPa).

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described the disclosed subject matter in general terms,reference will now be made to the accompanying drawings, which are notnecessarily drawn to scale, and wherein:

FIG. 1 is a block diagram of a catalytic biomass pyrolysis transportreactor system according to one embodiment of the present invention;

FIG. 2 illustrates a transport reactor loop useful according to oneembodiment of the invention;

FIG. 3 is a schematic of reaction processes believed to occur in thecatalytic biomass pyrolysis process according to certain embodiments ofthe invention; and

FIG. 4 is a graph of the temperature versus Delta G (Gibbs Free Energy)for various metal species in the deoxygenation of phenol to benzene.

DETAILED DESCRIPTION OF THE DISCLOSURE

The disclosed subject matter now will be described more fullyhereinafter through reference to various embodiments. These embodimentsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the subject matter to those skilled inthe art. Indeed, the disclosed subject matter may be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will satisfy applicable legal requirements. As usedherein, the singular forms “a”, “an”, “the”, include plural referentsunless the context clearly dictates otherwise.

The present disclosure provides processes for the production of abio-oil material from a biomass starting material. In certainembodiments, the processes can comprise reacting the biomass startingmaterial in the presence of a catalyst under pyrolysis conditionssufficient to transform the biomass starting material into a pyrolysisproduct, which can comprise a bio-oil. The pyrolysis productspecifically can comprise a solids fraction and a condensable vaporfraction, as well as a fraction of gases that do not condense at ambientconditions.

The present disclosure arises from the recognition that highly activeand selective catalysts are effective in manipulating biomass thermaldepolymerization to minimize char and light gas production whilemaximizing liquid bio-oil yields. In some embodiments, the disclosedsubject matter provides robust, integrated processes that can achievethe short residence times (e.g., about 0.5 to about 2 seconds) and highheat transfer rates for maximum liquid bio-oil yields while optimizingprocess integration to maintain catalyst activity by continuousregeneration. This combination can yield a condensed hydrocarbon liquid(bio-crude) that can be easily upgraded to fuels in the existinginfrastructure.

The disclosed methods also can be defined by an ability to selectivelyextract oxygen during pyrolysis and fix the oxygen, in part, in thesolid as metal oxides. This is in contrast to the conventional oxygenremoval as H₂O and carbon oxides (CO, CO₂), thus maintaining high carbonefficiency. The methods also can provide for higher catalyst activitycompared to the current catalysts in order to promote low-temperaturepyrolysis minimizing thermal cracking. Still further, the methods canmake use of multi-functional catalysts that can promote hydrocarboncondensation reactions. In certain embodiments, a fast fluidized bed ortransport reactor design can be used to provide adequate residence timesto limit thermal exposure and yet maximize vapor/catalyst contact time.

The terms “bio-oil” and “bio-crude” can be used interchangeably and areintended to mean the fraction of reaction products obtained from apyrolysis reaction that is liquid at ambient condition. The liquid-phaseproducts may comprise hydrophilic phase compounds, hydrophobic phasecompounds, or a mixture of hydrophilic and hydrophobic phase compounds.In certain embodiments, the bio-oil comprises a compound or a mixture ofcompounds such that the bio-oil is suitable for co-processing withtraditional crude oil in existing oil refineries. As such, the bio-oilpreferably comprises a compound or a mixture of compounds such that thebio-oil is suitable for undergoing further reactions, such asdistillation and/or catalytic processing, that transform the bio-oilinto a biofuel, such as bio-diesel, bio-gasoline, bio-jet fuel, or thelike.

Bio-oil is recognized as comprising a large number of differentcompounds. Table 1 provides the composition arising from typical,uncatalyzed fast pyrolysis of two types of wood at a temperature ofapproximately 500° C. (from Piskorz, J., et al., 1988, In Pyrolysis Oilsfrom Biomass, Soltes, E. J. and Milne, T. A., eds., ACS Symposium Series376).

TABLE 1 White Spruce Poplar Product Yields, wt % Water 11.6 12.2 Gas 7.810.8 Bio-char 12.2 7.7 Bio-oil 66.5 65.7 Bio-Oil Composition, wt %Saccharides 3.3 2.4 Anhydrosugars 6.5 6.8 Aldehydes 10.1 14.0 Furans0.35 — Ketones 1.24 1.4 Alcohols 2.0 1.2 Carboxylic Acids 11.0 8.5Water-Soluble - Total Above 34.5 34.3 Pyrolytic Lignin 20.6 16.2Unaccounted Fraction 11.4 15.2Approximately 35-40% by weight of the bio-oil derived from the typical,art-recognized, uncatalyzed fast pyrolysis reaction isoxygen-containing, water-soluble materials. The presently disclosedsubject matter provides a clear improvement upon the art because of theability to provide bio-oil as a pyrolysis reaction product that issignificantly lower in oxygen content and is much more suitable forrefining to form biofuels.

The biomass starting material used in the presently disclosed subjectmatter can comprise a wide variety of biological resources. For example,in some embodiments, the term biomass can take on the meaning set forthin the Energy Policy Act of 2005. Accordingly, the term “biomass” canmean: any lignin waste material that is segregated from other wastematerials and is determined to be nonhazardous by the Administrator ofthe Environmental Protection Agency and any solid, nonhazardous,cellulosic material that is derived from—(A) any of the followingforest-related resources: mill residues, precommercial thinnings, slash,and brush, or nonmerchantable material; (B) solid wood waste materials,including waste pallets, crates, dunnage, manufacturing and constructionwood wastes (other than pressure-treated, chemically-treated, or paintedwood wastes), and landscape or right-of-way tree trimmings, but notincluding municipal solid waste (garbage), gas derived from thebiodegradation of solid waste, or paper that is commonly recycled; (C)agriculture wastes, including orchard tree crops, vineyard, grain,legumes, sugar, and other crop by-products or residues, and livestockwaste nutrients; or (D) a plant that is grown exclusively as a fuel forthe production of electricity. Exemplary plants useful as a fuel forenergy production include switchgrass, miscanthus, energy canes,sorghum, willows, poplar, and eucalyptus.

In some embodiments, the biomass starting material can be any materialcomprising at least a fraction of a cellulosic and/or lignocellulosicmaterial. Cellulose is a polysaccharide formed of 1,4-linked glucoseunits and is the primary structural component found in plants. Celluloseis the most abundant organic chemical on earth, and there is anestimated annual biosphere production of approximately 90×10⁹ metrictons of the material. Lignin is a compound that is most commonly derivedfrom wood and is an integral part of the cell walls of plants. It is athree-dimensional amorphous natural polymer containing phenylpropaneunits that are tri- or tetra-substituted with hydroxyl groups andmethoxyl groups. Lignin makes up about one-quarter to one-third of thedry mass of wood and generally lacks a defined primary structure.Lignocellulose is primarily a combination of cellulose, lignin, andhemicellulose.

The biomass starting material particularly may comprise a wide varietyof cellulosics and lignocellulosics. For example, the biomass can bederived from both herbaceous and woody sources. Non-limiting examples ofherbaceous biomass sources useful according to the invention includewood (hardwood and/or softwood), tobacco, corn, corn residues, corncobs, cornhusks, sugarcane bagasse, castor oil plant, rapeseed plant,soybean plant, cereal straw, grain processing by-products, bamboo,bamboo pulp, bamboo sawdust, and energy grasses, such as switchgrass,miscanthus, and reed canary grass. Still further, useful biomass maycomprise “waste” materials, such as corn stover, rice straw, papersludge, and waste papers. The biomass also may comprise various gradesof paper and pulp, including recycled paper, which include variousamounts of lignins, recycled pulp, bleached paper or pulp, semi-bleachedpaper or pulp, and unbleached paper or pulp.

In the catalytic biomass pyrolysis process, biomass preparation cancomprise size reduction and drying of the biomass. Thus, the biomass canbe characterized as being particularized, which may be a natural stateof the biomass or may result from processing steps wherein a biomassmaterial is converted to a particularized form. Ideally, the size of thebiomass introduced into the reactor can be such that heat transfer ratesare high enough to maximize bio-oil production. Cost of size reductionand bio-oil yield preferably are balanced. In certain embodiments of thepresent process, biomass particles can have an average size of about 25mm or less, about 20 mm or less, about 10 mm or less, about 5 mm orless, about 2 mm or less, or about 1 mm or less. In specificembodiments, average particle size can be about 0.1 mm to about 25 mm,about 0.1 mm to about 20 mm, about 0.1 mm to about 10 mm, about 0.1 mmto about 5 mm, or about 0.1 mm to about 2 mm.

Moisture content of the biomass preferably is as close as possible to 0%by weight. In some instances, this may be cost prohibitive. Moisturecontent of the biomass can be adjusted external to the process orinternally by integrating a heat source to maintain the input biomass toa moisture content of about 15% or less, about 10%, about 7%, or about5% or less by weight.

Biomass pyrolysis can form a cocktail of compounds in various phases,and the pyrolysis product can contain in the range of 300 or morecompounds. In previous methods for the pyrolysis of biomass, thestarting material typically is heated in the absence of added oxygen toproduce a mixture of solid, liquid, and gaseous products depending uponthe pyrolysis temperature and residence time. When biomass is heated atlow temperatures and for long times (i.e., “slow pyrolysis”), charcoalis the dominant product. Gases are up to 80% by weight of the productwhen biomass is heated at temperatures above 700° C. In known methods of“fast pyrolysis” or “flash pyrolysis”, biomass is rapidly heated totemperatures ranging from 400° C. to 650° C. with low residence times,and such methods commonly achieve products that are up to 75% by weightorganic liquids on a dry feed basis. Although known methods of flashpyrolysis can produce bio-oils from various feedstocks, these oilstypically are acidic, chemically unstable, and require upgrading (asshown above in Table 1).

The present disclosure provides improved processes for biomass pyrolysisthat utilize specific catalysts and specific reaction conditions to formreaction products having a lower oxygen content compared to traditionalfast pyrolysis processes. Specifically, the reaction products in knownfast pyrolysis methods typically comprise from 35% to 50% by weightoxygen (i.e., oxygenated materials, such as esters, alcohols, aldehydes,ketones, sugars, and other oxy-compounds). The high oxygen content ofthe reaction products from known fast pyrolysis methods can contributeto the low stability of the reaction products and can complicateconversion of the reaction products into useful fuels, which typicallyare formed of mixtures of non-oxygenated, aliphatic and aromaticcompounds. Accordingly, pyrolysis processes that produce reactionproducts that are reduced in oxygen content (such as according to thepresent invention) allow for easier conversion of the reaction productto biofuels.

The presently disclosed subject matter particularly can be defined by areaction that is carried out under conditions (such as the presence of acatalyst as described herein, the use of a reaction temperature in arange described herein, and/or maintaining a reaction residence time asdescribed herein) that result in the formation of a reaction producthaving a low oxygen content. In specific embodiments, the oxygen contentof the reaction product can be about 30% or less, about 25% or less,about 20% or less, about 15% or less, about 10% or less, or about 5% orless by weight. In further embodiments, the oxygen content of thereaction product can be about 1% to about 25%, about 1% to about 20%,about 1% to about 15%, about 1% to about 10%, about 2% to about 10%, orabout 5% to about 10% by weight. The foregoing values are on a dryweight basis. In some embodiments, the reaction product in relation tooxygen content can comprise the totality of the non-solid fractionexiting the reactor. Thus, the disclosed subject matter can provide anon-solid reaction product fraction, wherein the non-solid reactionproduct fraction has an oxygen content as described above. The disclosedsubject matter also can provide a vapor and gas fraction of the reactionproduct, wherein the vapor and gas fraction has an oxygen content asdescribed above. In specific embodiments, the reaction product inrelation to oxygen content can comprise the bio-oil that is isolatedfrom the totality of the reaction product exiting the reactor. Thedisclosed subject matter can provide a bio-oil fraction of the reactionproduct, wherein the bio-oil has an oxygen content as described above.

The presently disclosed subject matter also is beneficial because thepyrolysis products require less additional processing that can reducecarbon conversion efficiency. For example, in removing oxygen from thereaction products in known pyrolysis methods, catalytic or non-catalyticmethods typically are employed that result in production of carbondioxide or carbon monoxide, which reduces the overall carbon content ofthe bio-oil that can be converted to a biofuel. Carbon conversionefficiency can be described as the amount of carbon in the isolatedbio-oil in comparison to the amount of carbon in the biomass startingmaterial, as defined by the following formula.

${{Carbon}\mspace{14mu} {Conversion}\mspace{14mu} {Efficiency}} = {\frac{{Mass}\mspace{14mu} {of}\mspace{14mu} {carbon}\mspace{14mu} {in}\mspace{14mu} {bio}\text{-}{oil}}{{{Mass}\mspace{14mu} {of}\mspace{14mu} {carbon}\mspace{14mu} {in}\mspace{14mu} {input}\mspace{20mu} {biomass}}\;} \times 100}$

This calculation does not include carbon from additional sources thatmay be used as feed for the generation of power, heat, or hydrogen inpotential process configurations of the present disclosure. Reducedcarbon content leads to a reduction in the total amount of biofuel thatcan be formed from the pyrolysis products. The catalytic pyrolysisprocess of the present disclosure can be defined by a carbon conversionefficiency of about 20% or greater, about 30% or greater, about 40% orgreater, about 50% or greater, about 60% or greater, or about 70% orgreater.

As described more fully herein, the catalytic pyrolysis process of thepresent disclosure achieves oxygen removal during the pyrolysisreaction, and the reaction products have an overall reduced oxygencontent. Such catalytic pyrolysis process may exhibit carbon conversionefficiency below that achievable by a fast pyrolysis process while stillproviding a resulting bio-oil defined by improved properties, including,without limitation, lower oxygen content, lower acidity, improvedthermal stability, and lower water content. Such improved propertiespositively affect downstream processing, and can significantly increaseyields of final products from upgrading of the bio-oil.

In certain embodiments, the catalytic pyrolysis process of the presentdisclosure can comprise reacting the biomass starting material underpyrolysis conditions in the presence of a catalyst to form a streamcomprising a pyrolysis product fraction and a catalyst fraction.Particularly, the pyrolysis product fraction (or a further fractionthereof) can have an oxygen content that is preferably below a certainamount, as described above. This is a particularly beneficial aspect ofthe reaction because the low oxygen content of the product increases theusefulness of the reaction product as a bio-oil—i.e., a greaterproportion of the reaction product is in a form that is useful as abio-oil.

FIG. 1 shows a block flow diagram of a catalytic biomass pyrolysisprocess 100 according to one embodiment of the present disclosure. Asshown therein, a biomass preparation unit 110 can be adapted forpreparing the raw biomass for the pyrolysis process, including sizereduction and drying of the raw biomass to the specifications otherwisedescribed herein. The prepared biomass can then be delivered as stream115 to a catalytic biomass pyrolysis unit 120 wherein the pyrolysisreaction can be carried out. Pyrolysis products as stream 125 then canbe delivered to a solid/vapor separation unit 130 where pyrolysis vaporsas stream 135 (including liquid fractions, if any are present) areseparated and sent to a vapor condensation/liquid collection unit 140,and solids as stream 137 (including catalyst and solid biomassfractions) are sent to a catalyst regeneration unit 150. In the catalystregeneration unit, biomass solids (e.g., ash) can be withdrawn as stream155, and catalyst as stream 157 can be sent to a reduction unit 160 toprepare the catalyst for reintroduction into the catalytic biomasspyrolysis unit as regenerated catalyst stream 165. Exhaust stream 159can be withdrawn as well and can comprise mainly CO₂. In the vaporcondensation/liquid collection unit 140, liquid bio-oil is formed andsent as stream 145 to a liquid separator 170 for separating the bio-oilproduct as stream 175 from water and other liquid components as stream177. Optionally, a hydrogen-rich tail gas can be withdrawn as stream 147from the vapor condensation/liquid collection unit 140 and used as acatalyst reducing agent and/or carrier gas. Such tail gas may beintroduced directly to the catalyst reduction unit 160 or into areducing gas stream 163 entering the catalyst reduction unit 160.

Any type of reactor useful for carrying out a typical fast pyrolysisreaction could be used according to the invention. Preferentially, thereactor is one that is adaptable to the use of a catalyst with theproperties discussed herein. Non-limiting examples of reactors thatcould be used in some embodiments of the invention include bubblingfluidized bed reactors, circulating fluidized bed/transport reactors,rotating cone pyrolyzers, ablative pyrolyzers, vacuum pyrolysisreactors, and auger reactors.

FIG. 2 shows a diagram of a catalytic biomass pyrolysis transportreactor system according to one embodiment that can be used to carry outprocesses as described herein. As illustrated, the prepared biomass isdelivered in stream 115 to a reactor and is optionally combined with acarrier gas. The biomass specifically enters a mixing zone of thebiomass pyrolysis unit 120 (a riser reactor in the exemplifiedembodiment) from where it is transported through a riser section of thereactor. One example of a material useful as a carrier gas according tothe invention is nitrogen gas. The carrier gas may be provided at asufficient rate relative to reactor diameter such that the biomass has aresidence time in the riser section of about 5 seconds or less, about 4seconds or less, about 3 seconds or less, about 2 seconds or less, orabout 1 second or less.

The biomass entering the riser reactor comes in contact with thecatalyst under the desired pyrolysis conditions, such as temperature,residence time, and catalyst to biomass ratio. In some embodiments,pyrolysis temperature can be in the range of about 200° C. to about 900°C., about 200° C. to about 700° C., about 200° C. to about 600° C.,about 200° C. to about 550° C., about 250° C. to about 500° C., or about300° C. to about 500° C. In specific embodiments, lower temperatureranges may be beneficial for minimizing undesirable thermal effects,such as cracking, and the use of specific catalysts may be beneficial insuch embodiments. For example, reacting of the biomass in the presenceof the catalyst can be carried out at a temperature of about 600° C. orless, about 550° C. or less, or about 500° C. or less. Residence time inthe reactor can be as noted above and, specifically, can be about 0.5seconds to about 5 seconds, about 0.5 seconds to about 4 seconds, about0.5 seconds to about 3 seconds, or about 0.5 seconds to about 2 seconds.

In specific embodiments, the pyrolysis reaction can be carried out atambient pressure. In other embodiments, the reaction can be carried outat an increased pressure, such as up to a pressure of about 35 bar (3.5MPa). In other embodiments, reaction pressure can be about ambientpressure to about 25 bar (2.5 MPa), about ambient pressure to about 20bar (2 MPa), or about ambient to about 10 bar (1 MPa).

The combination of the specific catalyst system and the desiredpyrolysis conditions are adapted to provide a robust, integrated processthat achieves the short residence times described herein and the highheat transfer rates necessary to maximize liquid bio-oil yield whileoptimizing process integration to maintain catalyst activity bycontinuous regeneration. The catalysts used herein may be any catalystuseful for selectively extracting oxygen during pyrolysis of thebiomass. For example, the catalysts may comprise a metallic element orcompound useful for removing oxygen from a fluidized system and fixingthe oxygen as a metal oxide. This is in contrast to conventional methodsfor oxygen removal (i.e., removal as H₂O, CO, and CO₂), and the presentinvention thus allows for maintaining high carbon efficiency. Thecatalysts of the invention also preferably have sufficiently highactivity to promote low-temperature pyrolysis, which can minimizethermal cracking of the reaction products. Multi-functional catalystsare useful to promote hydrocarbon condensation reactions. The type ofreactor used can be important for providing adequate residence times tolimit thermal exposure and maximize vapor/catalyst contact time foroxygen removal.

The catalyst can be regenerated in the catalyst regenerating unit orsection 150, as shown in FIG. 1 and FIG. 2. The regenerating reactor canbe, for example, a bubbling fluidized bed. Air, steam, or a combinationof air and steam, with and without an inert gas component such asnitrogen and/or carbon dioxide, can be injected into the regeneratingreactor to fluidize the catalyst bed, oxidize any char that is carriedover, and regenerate the catalyst by oxidizing surface carbon (e.g.,coke). The exothermic carbon oxidation also can impart heat into thecatalyst solids to drive the endothermic biomass pyrolysis reactions asthe catalyst is recirculated back to the mixing zone. No additional fuelmay be required to drive the process. All heat required for catalyticbiomass pyrolysis may be obtained from char and coke oxidation ifdesired.

Catalytic pyrolysis according to the disclosure can provide moreselective depolymerization and fragmentation of the cellulose,hemicellulose, and lignin components of the biomass at lowertemperatures. This combination of selectivity and lower temperatures canbe useful for increasing the bio-oil yield of the pyrolysis reaction.

As already described above in greater detail, known methods for removingoxygen from biomass pyrolysis vapors have included cracking over acidiccatalysts and hydrotreating over conventional hydrodesulfurization (HDS)catalysts. Such technologies, however, sacrifice hydrogen and carbon toeliminate oxygen in the form of water and carbon oxides. As pointed outabove, this reduces carbon conversion efficiency and thus reduces theoverall amount of biofuel that is formed. In contrast, the specificcatalyst used according to the present disclosure preferably is one thatselectively removes oxygen during biomass pyrolysis, controls biomasspyrolysis to inhibit char formation by targeting the scission ofspecific bonds in cellulose, hemicellulose, and lignin, and promoteshydrocarbon condensation reactions.

Catalysts used according to the disclosure can selectively remove oxygenthrough two simultaneous steps: 1) direct deoxygenation over a supportedmetal or reduced metal oxide catalyst with variable valence states; and2) indirect deoxygenation that utilizes catalytic hydrogen productionfor in situ hydrodeoxygenation. The general reactions believed to occurare schematically illustrated in FIG. 3, wherein M is a metal species asdescribed herein. Specific reactions for an iron oxide-based catalystare shown in Table 2. Similar reactions can be realized with furthermetal oxides in light of this disclosure.

TABLE 2 Regeneration Fe₃O₄ + CO → 3FeO + CO₂ Fe₃O₄ + H₂ → 3FeO + H₂ODeoxygenation (direct) 3FeO + ROH → RH + Fe₃O₄ Regeneration Fe₃O₄ + CO →3FeO + CO₂ Fe₃O₄ + H₂ → FeO + H₂O Deoxygenation (indirect) 3FeO + H₂O →H₂ + Fe₃O₄ ROH + H₂ → RH + H₂O Overall FeO + ROH → RH + Fe₃O₄

In specific embodiments, the catalyst used in the present disclosure maybe an iron-containing catalyst, such as an iron oxide material. Ironoxide based materials may be particularly useful because of the abilityto be continually regenerated as part of the pyrolysis cycle. Forexample, FeO may react with oxygen during pyrolysis to form Fe₃O₄. Inthis state, the catalyst may be reduced back to FeO prior to beingrecycled into the reactor for further reaction. Thus, the invention caninclude a catalyst regeneration cycle, wherein an oxidized catalyst iswithdrawn from the reactor, regenerated, and reduced prior to be beingintroduced back into the reactor. Many catalyst formulations can providehydrogen productivity and sustained lifetime through repeatedoxidation/reduction cycles. It is believed that these materials can actas a bifunctional catalyst to convert the water vapor formed duringbiomass pyrolysis into hydrogen to provide a reactive environment forhydrodeoxygenation and can also remove oxygen from biomass pyrolysisvapors without removing carbon.

The presently disclosed subject matter, in part, arises from therecognition of specific combinations of reactions that can be achievedwhen the correct pyrolysis conditions are provided while the biomassstarting material is reacted in the presence of a catalyst as describedherein. Solid acids have been found to be beneficial when incorporatedinto the pyrolysis system. For example, weak acids (such assilica-alumina materials) can function to catalyze dehydration anddecarboxylation of pyrolysis products, and strong acids (such asMFI-type zeolites) can function to catalyze alkylation, isomerization,and coking. Moreover, the redox loop illustrated in FIG. 3, whereintransition metals and oxides are continuously cycled, is believed to bea novel approach to biomass pyrolysis and provides a thermochemicallyfavorable operating window. Still further, it has been found that addinghydrogenolysis/hydrogenation components to the process allows for insitu H₂ consumption to assist deoxygenation.

In specific embodiments, the catalyst can be a bifunctional iron oxidebased material, such as described above, that is supported on anattrition-resistant material, such as a zeolite or any similarlyfunctioning material or may be a further, multi-functional material. Asnoted above, the choice of support material can affect the types ofreactions that occur during pyrolysis (i.e., choosing a weak acidsupport material versus a strong acid support material). Thus, anotherexample of a material that could be a useful support according to theinvention is a material comprising alumina alone or in combination withsilica. Of course, other catalysts, supports, and catalyst/supportcombinations that could be envisioned based on the description providedherein also could be used and are expressly encompassed by the presentdisclosure.

A thermodynamic analysis of further metal oxide materials that can beused according to some embodiments of the present disclosure is shown inFIG. 4, which specifically illustrates the effect of various metalcatalysts used for deoxygenation of phenol to benzene (i.e., an exampleof the conversion of ROH to RH, as shown in Table 2). The horizontaldashed line in FIG. 4 gives and approximate indication of the conditionsabove which only direct deoxygenation occurs and below which both directdeoxygenation and indirect deoxygenation occur. The illustratedtemperatures in the chart provide an exemplary embodiment of thetemperature range over which pyrolysis occurs.

The chart in FIG. 4 shows the relationship between reaction temperatureand Delta G (ΔG), or the change in Gibbs free energy in the system.Several metal or metal oxide species are shown to be useful fordeoxygenation by direct reaction (e.g., Co, Ni, CoO, and Mn) over thepreferred pyrolysis temperature range. Of the analyzed materials, Fe,FeO, and Sn were shown to be useful for both direct deoxygenation (i.e.,reaction with the metal) and indirect deoxygenation (i.e., reaction withhydrogen produced from the reaction of the metal with water vapor in thesystem). This illustrates that metal catalysts having a negative ΔG(T)for both steps of the redox cycle (metal oxidation and reduction) can beuseful as catalyst materials according to the present disclosure.Preferably, useful catalysts will have a ΔG that is less than about −67KJ/mol over the pyrolysis temperature range as such catalysts canprovide for both direct and indirect deoxygenation. Specific examples ofmetals that could be used in catalysts according to the presentdisclosure include manganese, iron, cobalt, nickel, copper, zirconium,molybdenum, palladium, tin, platinum, combinations thereof, oxidesthereof, and salts thereof. In preferred embodiments, a useful catalystcan comprise iron oxide or a bimetallic iron-tin oxide. In furtherembodiments, the catalyst may comprise a mixture of iron oxide and afurther metallic oxide promoter (i.e., a metallic oxide that enhancesreaction rate or improves product selectivity). Useful metallic oxidepromoters can include CrO₃, NiO, MnO, CoO, and MoO. Examples of specificiron-based catalysts that may be used according to the invention areprovided in U.S. Pat. No. 7,259,286, the disclosure of which isincorporated herein by reference in its entirety. The use of suchbifunctional catalysts are beneficial because they can function toconvert water vapor formed during biomass pyrolysis into hydrogen toprovide a reactive environment for hydrodeoxygenation and can removeoxygen from biomass pyrolysis vapors without removing carbon. Furtheruseful catalysts are described in U.S. Pat. App. No. 61/733,142, filedDec. 4, 2012, the disclosure of which is incorporated herein byreference in its entirety.

The amount of catalyst material circulated through the catalytic biomasspyrolysis process can be based upon the biomass throughput of thesystem. The amount of solid catalyst that is used can be an amountuseful to provide the needed heat of pyrolysis and to catalyticallycontrol vapor-phase chemistry, as described herein. In some embodiments,the amount of solid catalyst used (based upon the weight of the metalelement or compound separate from any support) can be such that theratio of catalyst to biomass is in the range of about 1:1 to about 100:1(based on mass). In other embodiments, the ratio of catalyst to biomassthroughput can be about 5:1 to about 75:1 or about 10:1 to about 50:1.

As the biomass and the catalyst react and move through the reactor,various reaction mechanisms are believed to occur, including but notlimited to the iron-steam reaction, the water gas shift reaction,catalytic deoxygenation of biomass pyrolysis vapors, andhydrodeoxygenation of biomass pyrolysis vapors. Catalyst deactivationalso may occur during the reaction arising from carbon deposition on thecatalyst surface. With reference again to FIG. 2, the stream 125 exitingthe reactor 120 (i.e., comprising circulating solids, vapors, and gases)is transferred to the separation unit 130 (a cyclone separator in theexemplified embodiment) that is used to separate the solids (e.g., spentcatalyst and char) exiting as stream 137 from the vapors and gasesexiting as stream 135.

Preferably, the catalyst used according to the present disclosure is aregenerable catalyst. Specifically, in embodiments wherein the catalystmay be at least partially deactivated, the catalyst used in theinvention can be regenerated to the active state (e.g., by removal ofdeposits, such as carbon). To this end, it is preferable for thecatalyst to be formed of a material such that the catalyst isinsensitive to the presence of materials that may lead to deactivationof the catalyst, such as ash. Regeneration of the catalyst moreparticularly can relate to the above-described process wherein thecatalyst that has been oxidized while catalyzing the pyrolysis reactionis further processed to reduce the material to the active state forreuse in the pyrolysis reaction.

After separation, the solids exiting the separator 130 in stream 137collect in a standpipe (not shown in FIG. 2) and flow into theregenerator reactor 150. Air, steam, or a mixture thereof is input tothe regenerator as stream 151 to oxidize any biomass char and coke thatdeposits on the catalyst surface. Primary regenerator products are CO₂(exiting with exhaust stream 159) and heat imparted to the regeneratedcatalyst exiting in stream 157. The CO₂ can be collected and removed forother use or sequestration.

In the embodiment illustrated in FIG. 2, the hot catalyst leaving theregenerator in stream 157 is transferred through a J-leg 158 into areducing zone or unit 160 located upstream from the riser reactor 120.In other embodiments, further configurations or components suitable forthe transfer of catalyst between the regenerator and the reducing zoneinclude, but are not limited to, L valves, Y leg, seal pots, and thelike. In the reducing zone, the catalyst is reduced by recirculating afraction of the tail gas stream 147 that exit the condenser system orunit 140 (described below). These gases are forced through a blower 180and pass as reducing stream 163 into the reducing zone 160 along withadditional carrier gas (e.g., CO and H₂) in stream 161, where thecatalyst is cycled back to its oxygen-reactive state. The combination ofgases and catalyst move through the reducing zone 160 and back into theriser reactor 120, preferably at a sufficiently high throughput toconvey the solids up the length of the reactor at high velocity toachieve the rapid heat transfer and short pyrolysis residence timedesired.

Returning to the cyclone separator 130, the mixture of pyrolysis vapors(in the gas phase) and gases that were separated from the solidsfraction immediately downstream of the reactor 120 are transferred to acondensation system or unit 140 where the vapors are condensed into aliquid (stream 145) that typically contains an aqueous phase and anorganic phase. The aqueous phase can be predominately water (e.g., about40% to about 99% water) with water-soluble organic materials such asacids (e.g., acetic acid), phenols, and unconverted anhydro-sugars. Theorganic phase typically has a much lower oxygen content than thewater-rich aqueous phase and different physical properties such asdensity, polarity, and/or other properties. The two phases arephysically separated (see unit 170 in FIG. 1), such as by knownseparation processes, and the hydrocarbon-rich bio-oil is collected atthe outlet (stream 175 in FIG. 1).

Also exiting the condensation system and product collection is afraction of permanent, reducing gases (i.e., the tail gases in stream147), such as carbon monoxide. The catalytic pyrolysis tail gas exitingthe condensation system (see FIG. 1) can be used for heat and powerproduction based on its heating value, but it can also be used to reducethe regenerated catalyst. Hydrogen and carbon monoxide are effectivereducing agents. Specific catalysts may promote the water gas shiftreaction resulting in a catalytic pyrolysis tail gas that is rich inhydrogen. This is also advantageous for catalyst regeneration.Therefore, the presently disclosed subject matter is particularlybeneficial by providing for the use of recycled tail gas or inputhydrogen to reduce a metal oxide catalyst before it is recirculated tothe mixing zone. At least a portion of the gases may be purged from thesystem (see stream 149 in FIG. 2).

Of course, it is understood that the systems described in relation toFIG. 1 and FIG. 2 are merely provided as an example of a catalyticbiomass pyrolysis system that may be used according to the invention.Other, similar systems may be used. Likewise, individual components ofthe described system may be replaced with other suitable means forproviding the same or similar function.

The present disclosure can be understood in specific embodiments asproviding a catalytic biomass pyrolysis process comprising reacting abiomass starting material under pyrolysis conditions in the presence ofa catalyst to form a bio-oil. Specifically, the formed bio-oil may havean oxygen content, as otherwise described herein. The bio-oil may bepresent in a vapor and/or gas phase and may be condensed to a liquidphase after the pyrolysis reaction. The catalytic biomass pyrolysisprocess may be defined as comprising forming a stream that comprises abio-oil containing reaction product and catalyst. The catalyst may beseparated from the bio-oil containing reaction product, and suchseparation further may include separating any solid component of thebio-oil containing reaction product. Thus, the method of forming abio-oil may comprise separating from the bio-oil containing reactionproduct any materials that are not liquid at ambient conditions. Themethod also may comprise regenerating the catalyst and recycling thecatalyst back into the catalytic biomass pyrolysis reaction. The methodalso may comprise separating from the bio-oil containing reactionproduct any material that is a gas at ambient conditions.

Beneficially, the bio-oil produced by the catalytic biomass pyrolysisprocess of the invention may be used directly as a refinery feedstock.As such, the bio-oil product may be blended at any ratio with petroleumcrude and likewise used as a refinery feedstock.

EXPERIMENTAL

The presently disclosed subject matter is more fully illustrated by thefollowing examples, which are set forth to illustrate the presentlydisclosed subject matter and provide full disclosure, and they are notto be construed as limiting thereof.

Example 1 Deoxygenation of Pyrolysis Vapors

To illustrate the effectiveness of metal oxide-based catalysts fordeoxygenation of biomass pyrolysis vapors, guaiacol (2-methoxy phenol)was introduced into a fixed bed microreactor packed with a reduced ironoxide catalyst. The iron oxide catalysts were reduced at 500° C. in 50%hydrogen for one hour prior to testing. Reactions were carried out at400-500° C. with a LHSV of 0.15 h⁻¹. Nitrogen was used as a carrier gaswith a flow rate of 90 cc/min with a 10 cc/min flow of argon as a tracergas. Reactor products were analyzed using an on line residual gasanalyzer with mass spectrometer. The major species identified fromguaiacol deoxygenation are reported in Table 3.

TABLE 3 Temp Conv. Major Products (wt %) (° C.) (%) Benzene ToluenePhenol Cresol CO CO₂ H₂O H₂ CH₄ Coke 400 48.6 0.3 0.9 3.1 2.0 1.8 6.611.5 0.0 0.4 22.1 450 73.7 0.6 1.0 12.4 3.4 5.6 9.6 14.8 0.1 1.2 25.1500 98 1.7 0.6 25.3 4.7 6.0 14.9 16.2 0.2 2.2 26.1

Removing the methoxy group from guaiacol is the most faciledeoxygenation pathway. The detection of alkyl phenols in the productindicates that oxygen can be removed from guaiacol using ironoxide-based catalysts without losing carbon (oxygen abstraction).Formation of cresol may have resulted from the alkylation of phenol bymethyl radicals and other alkyl groups generated when the methoxy groupis removed.

Reaction temperature had a significant effect on guaiacol conversion anddeoxygenated product distribution. Conversion increased from 49% (at400° C.) to 98% (at 500° C.). Product water content also increased withincreasing temperature, indicating that the dehydration activity of thecatalyst is increasing with temperature. Phenol is a major product atall reaction temperatures, along with other deoxygenated products.

Example 2 Catalytic Deoxygenation of Biomass-Derived Pyrolysis Vapors

A bench-scale pyrolysis unit was used to evaluate catalyticdeoxygenation with real biomass-derived pyrolysis vapors from a varietyof feedstocks. The unit had a maximum throughput of ˜500 g/hr ofpulverized biomass (212-500 μm particle size) metered through a twinscrew biomass feeder. The speed of the first screw was set to meter thefeedstock onto a second screw that transferred the feed to the inlet ofthe reactor.

The biomass feed dropped though a 1-inch diameter stainless tube into aneductor. A pre-heated dry nitrogen stream passed through the eductor,pneumatically conveying the biomass feedstock into and through theentrained flow pyrolysis section (a 17-ft, ⅜″-diameter stainless steeltube wound into a 3-ft high coil) placed inside a three-zoned furnacewith a maximum temperature of 1,200° C. Gas velocity was adjustablebetween 5 to 40 ft/sec by changing the nitrogen carrier gas flow rate.The biomass residence time through the system at normal operatingconditions was about 0.5-2 seconds.

Carrier gas, biomass pyrolysis vapors, and unconverted biomass char andash exited the bottom of the heated section into a heated cyclone forparticulate removal. The cyclone was 8-in long with a 2-in diameter by4-in long barrel designed to remove particles ≥10 μm with greater than90% efficiency. Char particles were cooled and collected for analysis.

Downstream of the cyclone was a 1-in.-diameter fixed-bed catalystreactor and a condensation system. The condenser was a shell-and-tubeheat exchanger design with a 2-in. diameter, 36-in. long inner tubesurrounded by a 3-in. diameter stainless steel cylindrical shell.Condensed bio-oils were collected at the outlet of the condenser in aglass bottle cooled in dry ice. The uncondensed aerosols and vaporsexited the condenser and were introduced into an impinger, also cooledin dry ice. The condensed products collected in these two vessels weremixed and analyzed. An on-line microGC was used to measure the permanentproduct gases. A gas sample was pulled through a filter, dried, andinjected onto the four GC columns. Permanent gases, up to C₆hydrocarbons, were measured in 3 minute cycles. Argon was introducedinto the carrier gas and used as an internal standard to determine theamount of gas phase products produced.

A baseline (uncatalyzed) bio-oil was produced from white oak pyrolysisat 500° C. with a residence time of 0.75 seconds in the pyrolysisreactor and cyclone removal of char. Physical and chemicalcharacteristics of the white oak feedstock, baseline bio-oil, andbaseline char are presented in Table 4 below. The high fixed carbon andlow oxygen content of the baseline char indicates near completepyrolysis. As expected, the ultimate analyses of the baseline bio-oiland the white oak feedstock are similar.

TABLE 4 Baseline Biomass Bio-Oil (White Oak) Baseline Char ProximateAnalysis (wt %) Volatile Matter 89.13 77.80 25.50 Fixed Carbon 10.9218.06 68.02 Ash 0.05 0.38 4.22 Higher Heating Value 7082 7940 11962(BTU/lb) Ultimate Analysis (wt %) Carbon 41.17 47.95 75.37 Hydrogen 7.486.06 3.25 Oxygen (by difference) 51.19 45.50 16.88 Nitrogen 0.09 0.100.26 Sulfur 0.01 0.01 0.02 Ash 0.05 0.38 4.22

The Fe-based catalyst was also tested in the bench scale pyrolysisreactor to determine its ability to deoxygenate actual pyrolysis vapors.Prior to pyrolysis testing the catalyst was reduced in a 5% H₂/balanceN₂ stream for two hours at 500° C. in a fixed bed reactor locateddownstream of the cyclone in the pyrolysis system. After catalystreduction, the temperature in the fixed bed reactor was lowered to 450°C. The pyrolysis conditions were identical to those used in producingthe baseline bio-oil from the white oak feedstock. Catalytic pyrolysisof biomass pyrolysis vapors was achieved for 30 minutes. 39.4-g ofbiomass was fed to the pyrolysis system and 10.0-g of bio-crude and 4-gof char were collected. Mass balance closure for this trial was 79.4 wt%. The gas yield during catalytic pyrolysis was more than 3 times highercompared to the baseline bio-oil production. Nearly 16 times more H₂ wasproduced during catalytic pyrolysis compared to non-catalytic pyrolysis,while the CO concentration was unchanged.

Ultimate analysis of the catalytically upgraded oil is given in Table 5.A significant reduction in oxygen content for the pyrolysis oil modifiedwith the Fe-based catalyst compared to the standard bio-oil wasobserved. The ash content of the upgraded oil was unusually highcompared to the baseline bio-oil. The high solids loading of thebio-crude is likely the result of catalyst carryover from the fixed bedreactor located upstream of the condensation train. The ultimateanalysis of the catalytically upgraded bio-oil was renormalized assumingthat the ash content was equal to the ash content measured for thebaseline bio-oil. These results suggest that the oxygen content ofbio-oil can be substantially reduced, by roughly 350%, using an ironoxide-based catalyst.

TABLE 5 Ultimate Analyses Catalytically Catalytically Upgraded (wt %)Upgraded Bio-Oil Bio-Oil (normalized) Carbon 48.4 74.99 Hydrogen 6.6210.26 Oxygen (by 9.26 14.36 difference) Nitrogen 0.11 0.17 Sulfur 0.090.14 Ash 35.55 0.05

Example 3

An iron-based catalyst suitable for catalytic fast pyrolysis of biomassaccording to the disclosure was prepared. In this embodiment, catalystpreparation was carried out by synthesis of a catalyst precursor, spraydrying of the catalyst precursor, and calcination.

The catalyst precursor was prepared by co-precipitation at a constant pHof 6.2 using 1.0-M solution containing Fe(NO₃)₃.9H₂O and Cu(NO₃)₃.2.5H₂Oin the desired Fe/Cu atomic ratio, which was precipitated by addingaqueous ammonium hydroxide solution. The resulting precipitate was thenfiltered and washed three times with deionized water. The potassiumpromoter was added as aqueous KHCO₃ solution to the un-dried,re-slurried Fe/Cu precipitate. This catalyst precursor was then slurriedwith polysilicic acid solution in a ratio effective to produce a finalcatalyst composition having 10 wt % SiO₂. The pH of the slurry was 6.4.Nitric acid was added to the slurry to reduce the ph to 1.5. A Niro Inc.spray dryer having a diameter of 3 feet and a height of 6 feet was usedto spray-dry the slurry. Finally the spray-dried catalyst was calcinedin an oxygen-containing atmosphere for 5 hours at 300° C.

Many modifications and other embodiments of the invention will come tomind to one skilled in the art to which this invention pertains havingthe benefit of the teachings presented in the foregoing descriptions andassociated drawings. Therefore, it is to be understood that theinvention is not to be limited to the specific embodiments disclosed andthat modifications and other embodiments are intended to be includedwithin the scope of the appended claims. Although specific terms areemployed herein, they are used in a generic and descriptive sense onlyand not for purposes of limitation.

1-32. (canceled)
 33. A catalytic biomass pyrolysis system comprising: areactor adapted for combining a biomass with a solid catalyst in areduced state under pyrolysis conditions to form a pyrolysis productstream; a separation unit in fluid connection with the reactor andadapted to form a first stream comprising a solids fraction from thepyrolysis product stream, said solids fraction comprising non-catalystsolids and solid catalyst, at least a portion of which is in an oxidizedstate, and a second stream comprising a vapors fraction from thepyrolysis reaction stream; a condenser unit in fluid communication withthe separation unit and adapted to condense a bio-crude from the vaporsin the second stream separate from a gas component of the second stream;an optional liquid separator unit in fluid communication with thecondenser unit and adapted to separate water or another liquid from thebio-crude; a catalyst regeneration unit in fluid communication with theseparation unit and adapted to remove the non-catalyst solids from thesolid catalyst present in the first stream; a reduction unit in fluidcommunication with the catalyst regeneration unit and adapted to reducethe solid catalyst that is in the oxidized state received from thecatalyst regeneration unit and provide solid catalyst in a reducedstate; and a catalyst delivery stream adapted to deliver the solidcatalyst in the reduced state from the reduction unit to the reactor.34. The catalytic biomass pyrolysis system of claim 33, furthercomprising an oxidant stream in fluid communication with the catalystregeneration unit and adapted to deliver an oxidant to the catalystregeneration unit.
 35. The catalytic biomass pyrolysis system of claim33, wherein the condenser unit is in fluid communication with thereduction unit via a gas flow stream adapted to transfer a portion ofthe gas component of the second stream to the reduction unit, andwherein the system optionally further comprises a blower unit interposedbetween and in fluid communication with the condenser unit and thereduction unit.
 36. (canceled)
 37. The catalytic biomass pyrolysissystem of claim 33, further comprising a biomass preparation unit influid communication with the reactor and adapted to transfer the biomassto the reactor, optionally wherein the biomass preparation unit isadapted to particularize a solid biomass to a size of about 25 mm orless.
 38. (canceled)
 39. The catalytic biomass pyrolysis system of claim37, wherein the reactor is adapted to combine the catalyst and thebiomass in a ratio of about 1:1 to about 100:1 based on mass.
 40. Thecatalytic biomass pyrolysis system of claim 33, wherein the reactor isone or more of: a transport reactor; adapted to accommodate flow of thebiomass therethrough with a residence time of about 5 seconds or less;adapted to function at a pressure of up to about 25 bar (2.5 MPa). 41.(canceled)
 42. The catalytic biomass pyrolysis system of claim 33,wherein the reactor is adapted to a function at a temperature of about200° C. to about 700° C. or a temperature of about 550° C. or less. 43.(canceled)
 44. (canceled)